Agricultural production is under constant stress from global population growth. Climate change, loss of arable land, and pathogenic parasites (insects and microorganisms) continually threaten agricultural production. New technologies, such as creation of transgenic plants and genetic inbreeding, have helped increase agricultural output, but are by no means a general solution. The high cost of fuel, fertilizers, and pesticides have also considerably increased the cost of food and endanger a constant food supply for the developing world.
Plants continuously respond to abiotic and biotic stress by adjusting their metabolism and activating diverse intracellular signaling responses. In particular, modifications of plant architecture in response to physical or chemical stimuli or the activation of pathogen-specific defense mechanisms upon microbial infection permits plant survival and reproduction. Classic signaling molecules, such as auxin, cytokinin, gibberellins, abscisic acid (ABA), and brassinosteroids, have been extensively studied in the context of their role in morphogenetic processes, whereas jasmonic acid (JA), ethylene, and salicylic acid (SA) have been found to participate in defense-responses against pathogens.
A novel group of lipid-derived plant metabolites, known as alkamides, has been shown recently to alter plant metabolism and development. Alkamides comprise over 200 related compounds that have been found in as many as 10 plant families: Aristolochiaceae, Asteraceae, Brassicaceae, Convolvulaceae, Euphorbiaceae, Menispermaceae, Piperaceae, Poaceae, Rutaceae, and Solanaceae. Plant-produced alkamides have been found to alter root and shoot system architecture in Arabidopsis by affecting cell division and differentiation processes. Morphogenetic responses affected by alkamides included primary root growth, lateral and adventitious root formation, root hair formation, and leaf development.
Alkamides have also been reported to have in vitro antimicrobial activity, in the absence of plants. For example, affinin has been demonstrated to inhibit the growth of some microbial plant pathogens, including bacteria and fungi. However, a reduced form of affinin, N-isobutyl decanamide, has been reported to lack a fungistatic activity that is present in affinin. In any event, relatively high levels of alkamides have been utilized to demonstrate in vitro antimicrobial activity, potentially making alkamides too expensive for large-scale use as antimicrobials.
Plants posses various inducible defense mechanisms to protect themselves against pathogen attack. For example, systemic acquired resistance (SAR) is activated in plants after infection by necrotizing pathogens. Similarly, colonization of plant roots by certain non-pathogenic rhizobacteria can elicit induced systemic resistance (ISR) in the host plant. ISR is a plant-mediated mechanism initiated at the root that extends up to the shoot. Similar to SAR, ISR is effective against different types of plant pathogens.
With the high cost and scarcity of food, increasing agricultural production and efficiency is key worldwide. Control of pathogens, especially bacteria and fungi, is important to enable increased production of food and better use of fertile land, but there is a growing awareness of the potential toxicity of standard pesticides. Thus, organically grown produce and grains are becoming important and growing markets. The use of natural, low cost pesticides, such as pesticides that induce natural defense mechanisms of plants, may significantly improve the outlook of the food supply worldwide and may, at the same time, provide eco-friendly pest control systems.